The present invention relates generally to operations performed and equipment utilized in conjunction with a subterranean well and, in an example described below, more specifically provides an internally oriented perforating apparatus.
It is sometimes desirable to perforate a well in a particular direction or range of directions relative to the wellbore. For example, in a deviated, inclined or horizontal well it is frequently beneficial to shoot perforating charges in a downward direction. However, certain circumstances may instead make it more beneficial to perforate in an upward direction, in a particular inclination from the upward or downward direction, or in another combination or range of directions.
To achieve this goal of perforating wells in particular directions, several attempts have been made to achieve reliable orientation of perforating charges downhole. Unfortunately, each of these has its drawbacks.
One method of orienting perforating charges downhole requires the charges to be rigidly mounted in a gun carrier so that they are pointed in the desired direction(s) relative to the carrier. The gun carrier is then conveyed into a wellbore and either laterally biased physically to one side of the wellbore so that the gun carrier seeks the lower portion of the wellbore due to gravity, or the gun carrier is rotatably supported with its center of gravity laterally offset relative to the wellbore. This method relies on the gun carrier rotating in the wellbore, so that the gun carrier may be oriented relative to the force of gravity. Frequently, such orienting rotation is unreliable due to friction between the gun carrier and the wellbore, debris in the wellbore, etc.
Another method of orienting perforating charges rotatably mounts the perforating charges in the gun carrier. The charges are mounted to a structure which extends substantially the length of the gun carrier. Rotating supports are attached at each end of the structure to permit the charges and the structure to rotate within the gun carrier due to gravity. Unfortunately, the structure is typically many feet in length and, with the charges mounted thereon, it tends to sag. This sagging of the structure permits it, or the charges mounted thereon, to contact the interior of the gun carrier. The contact prevents the charges from rotating in the gun carrier.
Therefore, an improved oriented perforating apparatus is needed. It is a purpose of the present invention to provide such an improved oriented perforating apparatus, as well as associated methods of perforating a well.
The principles of the invention are demonstrated below in an example of an internally oriented perforating gun which solves the above problems in the art by rotatably supporting the perforating charges periodically between ends of a gun carrier. This distributed rotational support prevents the charges, or their mounting structures, from contacting the interior of the gun carrier and preventing charge rotation. Well perforating methods are also provided.
In one aspect, a method of perforating a subterranean well is provided by the invention. The method includes the step of rotatably supporting multiple perforating charges within a single gun carrier by attaching at least one rotating support between selected ones of the charges. Each of the charges is directed in a respective direction. The gun carrier is conveyed into the well, with the gun carrier rotating as it is conveyed into the well. The perforating charges rotate within the gun carrier as the gun carrier rotates in the well, so that each charge remains directed in its respective direction.
In another aspect, a perforating gun for use in a well is provided by the invention. The perforating gun includes a generally tubular gun carrier, multiple perforating charges, at least one charge mounting structure for positioning the charges within the gun carrier, and multiple rotating supports permitting the charges to rotate within the gun carrier. At least one of the supports is connected between adjacent charges.
In yet another aspect, a perforating gun is provided which includes a generally tubular gun carrier, multiple charge mounting structures within the gun carrier, and at least a one rotating support connected between adjacent ones of the charge mounting structures.
The perforating apparatus provided by the invention may include a special thrust bearing for use between a charge mounting structure and a tandem, bull plug or other device attached to an end of the gun carrier. A specially configured weight may be used to laterally offset a center of gravity of a rotating assembly including the charges and mounting structure. The gun carrier may be provided with reduced wall thickness portions circumscribing the perforating charges, so that as the charges rotate within the carrier, each charge remains directed to shoot through one of the reduced wall thickness portions.
These and other features, advantages, benefits and objects of the invention will be clear to a person of ordinary skill in the art after careful consideration of the description of representative examples of the invention below and the accompanying drawings.